1. Field of the Invention
The present invention relates to improvements of a ribbon coil for a motor winding and it particularly relates to improvements of a wire end formation of the ribbon coil.
2. Description of the Related Art
Presently, a DC (Direct Current) motor, especially a brushless motor of coreless type, is widely used as a driving motor for driving a head cylinder and a capstan in a video apparatus and an audio apparatus to prevent noise derived from a brush and commutator system, and to prevent an irregular rotation due to the magnetic attraction and repulsion caused between the cores and magnets of the motor. In such a coreless motor, a ribbon coil is often used as a driving coil for the reason of easiness in the assembly process and for miniaturization of the motor.
FIG. 1 is a perspective view of a ribbon coil in a prior art. FIG. 2 is a perspective view of a ribbon coil in another prior art.
Generally, a ribbon coil 50 is constructed as a roll 54 by spirally winding a ribbon wire made of a narrow strip of metal foil 51 on which an insulation layer and a fusible layer 51a is coated in order, and the distal ends 52, 53 of the ribbon coil 50 are stripped by removing the insulation layer and the fusible layer 51a to form electrical terminals 52a, 53a for solderring lead wires (not shown), as shown in FIG. 1. However, as shown in FIG. 2, the ribbon coil 55 may be constructed in such a manner that wire ends 56, 57 of the ribbon coil 55 is pulled out of the roll 54 and is twisted 90 degrees in order to facilitate a subsequent wire end process. The wire end process includes a forming of electrical terminals 58, 59 on the wire ends 56, 57 of the ribbon coil 50 by removing the insulation layer and the fusible layer with a file and a cutter so that the wire ends 56, 57 are prepared for a subsequent solderring.
In the assembly process of the brushless motor, a plurality of the ribbon coils are disposed in a plane so as to form a circular stator (not shown), and a rotor having a plurality of permanent magnets (not shown) are rotatably provided in a manner that the permanent magnets face the ribbon coils.
In the prior art of FIG. 1, the wire ends 52, 53 of the ribbon coil 50 are not pulled out of the roll 54, in other words, they are adhered to the roll 54, so that it is difficult to form the electrical terminal 53a by using a cutter or a file in a small space 54a surrounded by the inside wall of the roll 54, this degrades a manipulating efficiency of the wire end process. Further, in solderring the lead wires, the electrical terminals 52a, 53a transfers heat easily to the roll 54, so that a solderring temperature is liable to change and is difficult to be controlled, which makes an electrical connection at a solderring joint unreliable. Furthermore, the adherence of the wire ends 52, 53 to the roll 54 poses a difficulty of determinating the front and back sides of the ribbon coil 50, which leads an erroneous mounting of the ribbon coil in the assembly process of the DC motor.
In the prior art of FIG. 2, the wire ends 56, 57 of the ribbon coil 55 pulled out of the roll 54, eliminate the above problems. However, it is difficult to cut the wire ends 56, 57 at desirable lengths and to remove the insulation layer and fusible layer therefrom. Especially, it is very difficult to manipulate the wire end 57 and to form the electrical terminal 59 within the small space 54a because available lengths of the wire ends 56, 57 are quite limited when the ribbon coil 55 is intended to be designed and made very small